U.S. patent application number 11/137270 was filed with the patent office on 2006-01-05 for digital manufacturing of removable oral appliances.
Invention is credited to James R. Kunkemoeller, Mark D. Lauren.
Application Number | 20060003292 11/137270 |
Document ID | / |
Family ID | 35451362 |
Filed Date | 2006-01-05 |
United States Patent
Application |
20060003292 |
Kind Code |
A1 |
Lauren; Mark D. ; et
al. |
January 5, 2006 |
Digital manufacturing of removable oral appliances
Abstract
A digitally-based method is described for the design and
production of customized removable dental appliances. The plastic
component of custom appliances is designed using software, and
milled directly over a plaster model of the dentition. A patient's
upper, lower, and bite-registered arches are digitized, registered
to a bite or centric occlusion position, and articulated in
software using either an average geometry or the geometry of a
specific articulator. Appliance design is performed by defining the
desired plastic surfaces and margins as dictated by the relative
movement and positions of the arches as functionally required for a
specific appliance. Standard CAM software is used to read the
design file and command a multiaxis machine center to mill the
plastic while directly on a plaster model.
Inventors: |
Lauren; Mark D.; (Amherst,
NY) ; Kunkemoeller; James R.; (West Seneca,
NY) |
Correspondence
Address: |
HODGSON RUSS LLP
ONE M & T PLAZA
SUITE 2000
BUFFALO
NY
14203-2391
US
|
Family ID: |
35451362 |
Appl. No.: |
11/137270 |
Filed: |
May 24, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60573690 |
May 24, 2004 |
|
|
|
Current U.S.
Class: |
433/215 ;
433/213; 433/24 |
Current CPC
Class: |
A61C 13/0004 20130101;
A61C 5/007 20130101; G16H 20/40 20180101; A61C 7/00 20130101; A61C
7/002 20130101 |
Class at
Publication: |
433/215 ;
433/024; 433/213 |
International
Class: |
A61C 5/00 20060101
A61C005/00; A61C 3/00 20060101 A61C003/00 |
Claims
1. A method of producing custom removable dental appliances
comprising: a) obtaining a 3-dimensional digital record of the
upper and lower dentition, including a combination record, said
combination record consisting of 3-dimensional digital data that
represents the upper and lower arches together in either a bite
position or centric occlusion; b) registering the upper and lower
models using the combination record as reference to produce a
digital record of the complete upper and lower dental arches
approximated in either a bite or centric occlusion relationship; c)
using software to articulate the upper and lower models in a
computer to enable sufficient repositioning of the models to
facilitate the design of a removable dental appliance; d) using
software to design the surface and margins of the plastic component
of a removable dental appliance and produce an associated
3-dimensional data file; and e) using CAM software to read the
design file and generate the tool paths required to mill the
desired plastic shape using a machine center.
2. The method according to claim 1 wherein the appliance is an
occlusal splint, orthodontic retainer, sleep apnea appliance, or
Herbst framework.
3. A removable dental appliance made according to the method of
claim 1.
4. The method according to claim 1 wherein the 3-dimensional record
of the dentition is obtained by laser scanning plaster models
mounted to plastic articulator bases; the registering of the upper
and lower models is facilitated by target markers applied or
related to the upper and lower models prior to digitizing;
5. The method according to claim 1 further comprising providing
software to a doctor to facilitate his providing digital design
information related to the articulation or design of a
patient-specific removable dental appliance.
6. The method according to claim 1 wherein the milling of the
desired plastic shape is performed.
7. The method according to claim 1 wherein the design of the
appliance comprises: a) controlling the degree of undercutting of
the plastic to ensure a proper fit to the patient, b) moving an
occlusal plane down over the surface of a model to identify points
of first contact on cusp tips to aid in the design of occlusal
splints, and c) identifying the location of wires in an appliance
to avoid cutting the wires during the milling process.
8. The method according to claim 1 further comprising smoothing the
machined plastic surface using an abrasive tool in the milling
machine to provide a finer surface finish.
9. The method according to claim 1 wherein the milling machine is a
3, 4, or 5 axis machine center.
10. The method according to claim 1 further comprising adapting
plastic to a dental model to allow the excess to be milled away to
produce the desired dental appliance, said plastic ranging from
hard acrylic to soft silicone, and including thermoformed material
as part or all of the plastic component.
11. A computerized method of producing removable dental appliances
comprising: a) producing a 3-dimensional digital representation of
a patient's dentition and oral soft tissue; b) utilizing the
digital representation to simulate functional movements required
for an appliance design; c) utilizing the simulated functional
movements to provide a design file describing surface geometry and
margins of an appliance; and d) utilizing the design file to
produce machine tool paths to make the appliance.
12. The method according to claim 11, wherein the digital
representation includes upper and lower jaw models and a
combination model thereof.
13. The method according to claim 11, wherein simulation of
functional movements includes modeling the patient's
articulation.
14. The method according to claim 11, wherein the surface geometry
and margins are defined relative to occlusal planes, surface height
and contour in relation to an opposing arch and contact points and
sliding arcs on an opposing arch.
15. The method according to claim 11, wherein the machine tool
paths are utilized by a multi-axis milling machine.
16. A removable dental appliance made according to the method of
claim 11.
Description
CROSS REFERENCE TO A RELATED APPLICATION
[0001] Applicants claim priority based on provisional application
No. 60/573,690 filed May 24, 2004 and entitled "Digital
Manufacturing Of Oral Appliances" which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] This invention relates to the art of dental appliances, and
more particularly to a new and improved method of making removable
dental appliances.
[0003] Dental appliances make up a diverse group of devices ranging
from ceramic orthodontic brackets to soft mouth guards. Some are
custom-fitted devices and some are supplied generically to fit a
variety of patients. A distinct subgroup of custom-fitted
appliances consists of appliances that are removable from the
mouth. As a group, removable appliances include orthodontic
retainers, occlusal splints, palatal expanders, Herbst appliances,
and appliances to relieve sleep apnea. They are produced in
commercial dental laboratories as well as in office dental
laboratories. As a group, removable appliances provide tooth
immobilization, occlusal protection, relief of TMD symptoms,
repositioning of the mandible, palatal arch expansion, and other
gross dental/skeletal therapeutic actions.
[0004] Removable dental appliances are typically made by adapting
plastic to a stone model of a patient's teeth. Both hard and soft
polymers are used, such as acrylics and silicones. The most
commonly used system is methylmethacrylate monomer and polymer
(cold cure acrylic). Thermoformed materials are also used. Such
appliances also usually incorporate metal as wire, springs, custom
fabricated frameworks, pivots, beams, and other mechanical
elements. Round wire is typically used to fashion clasps for
retention, and for strength.
[0005] Removable appliance fabrication typically starts with
bending and placing the required wires onto a model. The wires are
then embedding in acrylic to form the body of the appliance. The
plastic is usually applied in excess, which is then manually
trimmed to the desired surface contour, and final polished.
Trimming is performed using large bench-mounted abrasive wheels,
motorized lathes fitted with stone wheels, and manually-held
handpieces. Following trimming, the appliance is typically finished
using wet pumice and increasingly fine buffing and polishing
steps.
[0006] While technicians generally follow specific guidelines for
trimming removable appliances, the process remains an art to a
certain degree. Applying extra plastic to a model requires less
time and skill than minimizing excess, thereby increasing trimming
requirements. The quality of the finished product depends upon a
technician's skill and attention to detail. Person-to-person
variation in quality and speed exists.
SUMMARY OF THE INVENTION
[0007] This invention provides pc-based methods for designing and
trimming the body of removable dental appliances. Appliance design
is performed in a computer, and computer-controlled machines are
used to mill the body of the appliance. The advantages include
improved uniformity of design and final shape, reduced trimming
time, integration with digital diagnostic information to enhance
design, and ability to provide digitally-based design input from
the prescribing doctor.
[0008] The methods of this invention are based upon the following
basic process: [0009] 1. Modeling the Dentition [0010] Producing a
3-dimensional (3D) representation of a patient's dentition and oral
soft tissue in a computer. [0011] 2. Appliance Design [0012]
Software is first used to articulate the models to allow the
simulation of functional movements required for appliance design.
Custom software is then used to design the appliance. A computer
file is produced that describes the desired surface geometry and
margins of the appliance. [0013] 3. Appliance Production [0014]
Standard CAM software is used to read the design file so generated
and produce the machine tool paths required to mill the desired
plastic component or appliance.
[0015] Turning first to modeling the dentition, the 3D
representation of a patient's oral structures may be produced by a
number of methods well known in the art, for example: [0016] a)
Optically scanning a stone model produced from an oral impression,
[0017] b) Using serial section destructive techniques, [0018] c)
Directly scanning the mouth, or [0019] d) Scanning an oral
impression Each of these methods, and others, are appropriate for
producing a digital representation of a patient's dentition
suitable for appliance design. The specific method and file type
generated is not important to the execution of this invention.
[0020] Typically, individual upper and lower models are scanned. A
combination scan is also performed of both models together (either
in centric occlusion or with a bite in place). These three files
are generally sufficient to then articulate a case. Facebow mounted
models (for a specific articulator) may also be used by referencing
the 3D data to the model's mounting plate, and dimensionally
relating the plates to any specific articulator. Any condylar hinge
geometry may be included in the articulation.
[0021] Turning next to appliance design, it is concerned with
defining the plastic components of an appliance, which requires
custom software. If the upper and lower models must be articulated,
then articulation is performed by computer prior to design. A
computer file is produced which represents the desired shape
(surface and margins) of the appliance. For a basic occlusal
splint, the design process produces a standard 3D file (*.stl or
*.iges) that can be displayed as a 3D object in a computer or
imported into CAM software for manufacturing.
[0022] Broadly, the user first selects the type of removable
appliance to be designed. Then, key anatomic locations on the 3D
model are identified by clicking on the model on the computer
screen. These points are used to construct the 3D surface of the
device based upon specific dental rules or design algorithms. These
algorithms can serve as templates to facilitate the design of
specific classes of appliances. The plastic thickness at a
specified location or the desired contour over a specified area may
be automatically generated. Software also provides the capability
of modifying the surface and margins.
[0023] A generalized description of the basic design tools is
provided. These tools are combined to create design software
specific to a single type of appliance. In a preferred embodiment,
appliance design software utilizes tools that include: [0024]
Modeling the articulation to allow the lower arch to be moved. This
is required when modeling the arcs and paths of tooth movement in
response to appliance-specific excursions of the mandible. [0025]
Defining the margins of an appliance by clicking a series of points
on the 3D model. [0026] Defining and moving occlusal planes. [0027]
Extending surfaces off the dental model that are bordered by the
appliance margin. [0028] Modifying the height and contour of the
extended surface in relation to the opposing arch. [0029]
Identifying contact points and sliding arcs on an opposing arch.
[0030] Software to consider the location of wires in an appliance
during trimming The computer file so produced contains the 3D
information describing the appliance surface and margins to be
trimmed.
[0031] Turning finally to appliance production, the specific type
of plastic for a removable appliance is adapted to a plaster model
in excess which is milled away to produce the desired appliance
surface. Standard CAM software may be used to convert the design
file into the required tool paths to mill excess plastic and
produce the desired surface. Since the plastic is already adapted
to the complex anatomy of the teeth, detailed dental anatomy does
not have to be milled. This greatly reduces the size of the design
file and the complexity of the geometry to be machined. Typically,
a multi-axis machine center is used to mill the appliance. A three
axis system may be capable of producing the majority of cases,
while a four or five axis system is required to produce undercut
regions.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
[0032] FIG. 1 is a block diagram of the basic processes of this
invention using an occlusal splint as an example.
[0033] FIG. 2 is a computer image of an example combination scan.
This image shows a single front laser scan of two models placed in
centric occlusion. The upper model (10) and lower model (20) are
shown together. The upper model is marked with crosses (30) to aid
with registration. The lower model is marked with open circles
(40). Sufficient detail is captured of the upper and lower models
to allow registration of the upper and lower complete scans.
[0034] FIG. 3 is a computer image which illustrates complete upper
and lower models (60) registered to each other according to the
combination scan in FIG. 1. The occlusal plane of the lower model
is also shown (50). Two separate files (upper and lower complete
model scans) are shown together.
[0035] FIG. 4 is a diagrammatic right saggital view diagramming the
geometric parameters used to establish the hinge axis for unmounted
models using a lower model. A cusp on a distal molar (100) and the
tip of a central incisor (110) are used to establish a lower
occlusal plane (120), which is set to a default angle (130) of
15.degree. to the horizontal. The axis-incisal distance (140) is
defaulted at 100 mm and the vertical height (150) is defaulted to
50 mm. The condyle is modeled as a sphere (160). The concylar
inclination angle (170) is defaulted to 20.degree. to the
horizontal, and a typical eminence curve is shown as (180).
[0036] FIG. 5 is a computer image which illustrates how
user-defined points (70) may be located on the teeth to define the
margin of the appliance. A spline (80), or other form is generated
between the contact points. The curvature, or degree to which the
curve adheres to the points, is software controlled. This method
may be used to control the degree of undercutting. In this case,
the spline (80) is designed offset (90) from the tooth
surfaces.
[0037] FIG. 6 is a computer image which illustrates the application
of PMMA acrylic (190) to half the arch of a plaster dental model
(200), capturing the details of the teeth. Excess plastic is
applied to allow for milling. The adaptation of acrylic or other
plastics to the models is performed using standard laboratory
methods.
[0038] FIG. 7 is a computer image which shows a centric relation
splint (210) produced by the methods of this invention.
DETAILED DESCRIPTION
[0039] While the basic method described in the foregoing Summary of
is applicable to a variety of removable appliance types, details of
modeling the dentition, appliance design, and appliance production
are described using an occlusal splint as an example. The process
for producing an occlusal splint is summarized in FIG. 1. Digital
3D files of the upper, lower and combined models are designated 1a,
1b and 1c in FIG. 1. Registration of the individual upper 1a and
lower 1b models to the combination scan 1c is represented at 2. The
first step in appliance design, articulation, is shown at 3, and
the design process is shown at 4. Appliance production includes
generating tool paths 5, applying plastic 6 and milling 7.
[0040] Turning first to modeling the dentition, several methods are
known in the art for creating a 3D representation of dental anatomy
in a computer with sufficient detail to carry out this invention. A
preferred method for obtaining a 3D representation of (digitizing)
a patient's teeth and soft tissue is laser scanning plaster models.
Plaster models are mounted on standard articulator mounting plates
to allow easy and accurate relocation from the scanning system to a
mounting jig in the machine center. Magnetic attachments may be
used. In a preferred embodiment, unmounted lower and upper stone
models are plastered to standard bases typically used to attach to
dental articulators. Mountings are simply done to a convenient
level position. Cases already mounted for a specific articulator
are scanned in a similar fashion. These cases, however, have
built-in articulation relationships determined by the geometry of
the articulator used.
[0041] An important aspect of digitizing is having the models in a
specific coordinate system. It is critical that that the appliance
is designed and machined in coordinate systems with a known
relationship to each other. The model mounting plate is a
convenient reference to use. This reference allows the arches to be
re-positioned in a computer to duplicate their relative positions
when placed on any articulator. The model base reference also
provides convenient work planes for machining. The identification
and definition of this coordinate system is performed by scanning a
calibration block whose surfaces can be related to the model base.
For a rotary laser scanning system, one of the scans is performed
in an identical position as the calibration block. This scan then
serves as the fixed object to which subsequent scans are registered
and merged. This method produces digital 3D files of the upper,
lower, and combined models with a consistent coordinate system
amenable for articulation, design, and machining. Thus the
combination scan of FIG. 2 shows the upper 10 and lower 20 models.
In general, models may be transformed to alternate original
coordinate system to suit typical variations of the given
method.
[0042] Another important feature of digitizing is the registration
of the individual upper and lower models to the combination scan.
Such registration is shown in FIG. 3. Registration may be
accomplished by a variety of well known surface matching
techniques. These methods are typically based on: 1) defining the
combination scan as a fixed object and either the upper or lower
model as a floating object, 2) identifying corresponding points on
the fixed and floating objects, and 3) comparing the surfaces
surrounding these points to align and reorient the objects. A
system of colors, crosshairs, or other recognizable optical targets
may be used to provide the means for more automated registration.
By way of illustration, the crosses 30 and circles 40 of FIG. 2
function as such registration aids.
[0043] Turning next to appliance design, similar design tool and
procedures are used for all removable appliances. The first step,
if needed, is always articulation. Sufficient articulation geometry
must be defined for design to take place. This information is
typically the location of a hinge axis and modeled condylar
detail.
[0044] The generalized design process of this invention involves
the following elements. Some appliances do not require the use of
all of these design elements: [0045] Evaluation of mandibular
repositioning and excursions--The lower dental arch is moved in
concert or repositioned to simulate positions for appliance design.
This process models in space the arcs and swept surfaces of tooth
movement in response to mandibular excursions. [0046] Defining
occlusal planes on the digital models to provide reference surfaces
for design. [0047] Defining an appliance margin using a template of
points that automatically generates the desired perimeter. [0048]
Building surfaces off the dental model that are bordered by the
appliance margin. [0049] Identifying tooth/appliance contact points
and surfaces based upon an opposing arch. [0050] Defining appliance
margins by clicking points on the 3D model. [0051] Identifying the
location of wires in an appliance during trimming. Wires that are
imbedded in plastic should have known or assumed distances from the
surface. Wires that extend out of the plastic surface should have
known locations. The registered upper and lower scans are read into
custom CAD software that allows a user to articulate the models and
design an appliance. The result of appliance design is a computer
file that contains the 3D information describing the desired
appliance surface and margins.
[0052] Removable appliance design typically begins with
articulation. Articulation may be performed in a variety of ways
based on slightly different dental rules. In a preferred
embodiment, articulation is considered for mounted and unmounted
cases. Mounted cases are models that are provided to the laboratory
already plastered to a mounting for a particular articulator. A
bite registration may also be provided. A doctor has typically
taken a facebow recording of the true position of the upper and
lower dental arches relative to the cranium, and transferred that
position to the mounting. This mounting therefore contains all the
jaw orientation data required for articulation when the models are
positioned as they would be on a particular articulator. This is
done in a computer by simply modeling the geometry of a particular
articulator, which may include articulation joint geometry.
Rotating and or translating the lower model relative to the fixed
upper is then performed to simulate classically mounted models.
[0053] Unmounted cases are provided to the dental laboratory as
either impressions or plaster models. A bite registration may be
provided. The articulation of unmounted cases is more involved
since the mounts do not contain any patient-specific information.
In a preferred embodiment, unmounted cases are articulated to an
average geometry. Models are poured to a convenient low height and
are plastered to a standard articulator base plate in a generally
horizontal position. Upper, lower, and combination scans are
obtained.
[0054] In a preferred embodiment, unmounted models are articulated
in the computer as follows. Following registration of the upper and
lower models to the combination scan, an occlusal plane is defined
on the lower model. This may be done by identifying three points on
the lower model and calculating the resultant plane. Typically, the
distal buccal cusps of the left and right second molars are used as
well as the midline tip of the central incisors (for example, 100
and 110 in FIG. 4). The jaw midline should be used and not the
dental midline if they are significantly different. The lower
occlusal plane (120 in FIG. 4) is then inclined at a settable angle
to the horizontal, typically about 150 (the angle 130 in FIG. 4).
To locate a hinge axis, two additional pieces of information are
used: 1) the tip of lower central incisor is located at a point
(settable) about 100 mm normal to the hinge axis (140 in FIG. 4),
and 2) the vertical height from the incisal tip to the hinge axis
(settable) is about 50 mm (150 in FIG. 4). The occlusal plane
angle, axis-incisal distance, and vertical height are used to
establish the location of a hinge axis.
[0055] No additional articulation geometry is required for the
design of flat plane splints, and the condyle maybe modeled as a
simple hinge in centric relation. Centric relation splints and
other appliances require more detailed modeling of the TMJ.
[0056] More detailed modeling of the TMJ is required to design
centric relation splints since the mandible must be translated
anteriorly as well as side-to-side. At least three additional
parameters may be built into the TMJ modeling: the condylar
inclination angle (170 in FIG. 4), an eminence ramp (180 in FIG. 4)
along the condylar incline, and a sideways Bennet angle function.
Some fully-adjustable articulators allow these three parameters to
be set. Similarly, specific geometry may be modeled to duplicate
the settings of specific mechanical articulators.
[0057] The tooth contact surface is the most important of aspect of
an occlusal splint. Following articulation, the next step in splint
design is establishing desired bite opening. With both models
articulated and visible on a computer screen, the lower jaw is
rotated around the hinge axis to open the bite. The models are
typically viewed from the left or right buccal side so as to look
through the occlusion. This view allows the user to visualize the
open space across the arches, ensuring sufficient plastic thickness
over the teeth and the absence of side to side sliding
interferences. A measuring tool in software may be used to measure
distance on the computer screen. Alternatively, software may be
used to open the bite a minimum specified distance. Once the bite
is set, the splint is designed and built to that opening.
[0058] The location of the contact points of the teeth of the
opposing arch is then determined to establish the occlusal surface
of the splint. All teeth should contact the splint surface when the
mouth is closed in centric rotation. The contacts on the opposing
teeth may be locating by: [0059] 1) manually clicking on a model
surface to identify a location, [0060] 2) using software to
optimize manually positioned points by relocating the point to the
most occlusal location on the tooth parallel the occlusal plane, or
[0061] 3) passing an occlusal plane through a model surface to
identify the cusp locations that first break through the moving
plane Centric relation splint design requires the lower arch to be
moved through a variety of excursions to identify the sliding
surfaces required to ensure desired disclusion of the posterior
teeth when the jaw is moved (left to right as well as normal
opening). These motions are readily simulated in the computer since
all of the needed geometry exists to identify the required pivot
points and angles. The appliance occlusal surface is designed to
have point contact of the posterior teeth (bicuspids back) and a
gliding or line contact of the anterior teeth.
[0062] Joining the appliance occlusal surface with the appliance
margin is an important process. Penetration into the interproximal
region is also controllable. The desired degree of interproximal
penetration varies with appliance type and design for specific
patients. Consideration of the path of insertion may be used to
control the degree undercuts to be overcome by the appliance during
insertion by the patient. Different appliance materials have
different abilities to fit over undercuts. When the joining the
appliance occlusal surface and margin is complete, a computer file
is created that describes the margins, sides, and occlusal surfaces
of the appliance. As shown in FIG. 5, points 70 define the margin
of the appliance, and a spline 80 is designed with offset 90.
[0063] Turning finally to appliance production, production of the
desired appliance, or appliance component, is preferably achieved
by commanding a machine center to mill the excess plastic over a
physical model, for example acrylic 190 applied to model 200 in
FIG. 6. Commercially available CAM software may be used to read the
design file and generate the appropriate tool paths needed for
milling. The optimum combination of tool shapes, tool paths, and
speeds is a tradeoff between trimming time and the required surface
finish.
[0064] In a preferred embodiment, when machining soft
heat-sensitive polymers, the work piece may be cooled with air or
liquids to prevent the material from heating. In another alternate
embodiment, the model may scanned following application of the
initial plastic to determine the amount and shape of the material
to be removed. This can help optimize the choice of tools and tool
paths, particularly for initial roughing.
[0065] While embodiments of the invention have been described in
detail, that has been done for the purpose of illustration, not
limitation.
* * * * *